Chapter49 The%2 - BLY 122 Summer 2006 Chapter 49 The Immune System in Animals I Innate Immunity A A Hunter from C S Major Early Observations of

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1 BLY 122 Summer 2006 A. Hunter from C. S. Major Chapter 49 The Immune System in Animals I. Innate Immunity A. Early Observations of Immunity 1. Three observations in determining how immunity works: a. Wounds usually heal even if they become infected. b. People infected with a virus or bacteria usually recover even without drugs. c. People who have been infected with a disease rarely get the disease again. 2. E. Jenner (1700s) had a key insight. a. Jenner hypothesis: Milkmaids did not get smallpox because exposure to cow’s milk exposed them to cowpox, which was providing immunity. b. Experiment: Inoculate a boy with fluid from a cowpox pustule, then later inoculate with fluid from a smallpox pustule. c. Result: The boy did not get smallpox. d. Jenner’s technique, vaccination, was adopted throughout Europe. B. Cells that are always ready to respond to foreign invaders confer innate immunity. 1. Antigens are any foreign molecule. a. Most are proteins or glycoproteins from bacteria or viruses. b. Foreign carbohydrates or lipids can also act as antigens. 2. Cells involved in innate immunity are nonspecific in their response to antigens. 3. Innate response is the same regardless of the species of organism that invades. C. Barriers to Entry 1. Human skin provides a physical and chemical barrier. a. Lactic acid and fatty acids lower the pH of the surface and inhibit bacteria. b. Protective mucus on the skin surface prevents contact of pathogens with skin cells. 2. Breaks occur in the skin barrier. a. Breaks in the barrier occur at openings of the digestive, reproductive tracts, respiratory tracts, and sense organs. b. Some viruses have an enzyme that breaks down the mucus barrier. c. Eyes are protected by tears, which have lysozyme that will break down bacterial cell walls. D. The Innate Immune Response 1. Leukocytes implement the innate response when infection occurs. 2. Pattern recognition receptors on immune cells detect molecules unique to invaders: a. N -formylmethionine on bacterial proteins b. Lipopolysaccharide in walls of gram-negative bacteria c. Cell-wall components that terminate in mannose 3. The inflammatory response is activated: a. Platelets form clots in places where skin has broken and bleeding occurs. b. Mast-cell leukocytes release chemicals that cause blood vessels near the wound to constrict. c. Other mast-cell secretions cause vessels farther from the wound to dilate. d. Blood delivery to the wound area increases. e. Cells in nearby tissues release chemokines.
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2 f. Chemokines create a chemotactic gradient that neutrophils and other leukocytes use to find the wound site. g. Neutrophils phagocytose bacteria and secrete lysozyme, which degrades bacterial cell walls. h.
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This note was uploaded on 11/11/2009 for the course BLY 459 taught by Professor Obrien,j during the Spring '08 term at S. Alabama.

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Chapter49 The%2 - BLY 122 Summer 2006 Chapter 49 The Immune System in Animals I Innate Immunity A A Hunter from C S Major Early Observations of

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